screen is blank / "jack fail" after boot with 2+ USB devices

[catfact]

lines thread: https://llllllll.co/t/norns-screen-goes-blank-after-boot-up/38566/30

in summary:

• occasionally when booting with 2 or more USB devices (including WIFI dongle,) norns appears to halt after the bootup animation, displaying a blank screen and not responding to key presses

• normal operation resumes (sometimes?), showing the SELECT menu, when one device is removed.

• occurs on wall and battery power

• might occur more often with monome grids. but we have reports with many other devices (mostly MIDI.)

• the one journalctl output we have so far does show URB error; this is with an FTDI gri:

  [ 377.280744] ftdi_sio ttyUSB0: usb_serial_generic_write_bulk_callback - urb stopped: -32

[catfact]

this has to be some kind of power starvation affecting the usb bus/hub. its not really something addressable in the norns stack (AFAICT, maybe we'll get some kind of usb draw monitoring?) leaving as known issue

[tehn]

shield specific, i might add

[tehn]

or, as it happens, some occurrences noted on standard norns as well. sorry